Frank J. Wilson (May 19, 1886 – June 22, 1970) was the Chief of the United States Secret Service and a former agent of the Treasury Department's Bureau of Internal Revenue, later known as the Internal Revenue Service, most notably in the 1931 prosecution of Chicago mobster Al Capone and federal representative in the Lindbergh kidnapping case.

In 1928, Wilson was assigned by the chief of the Enforcement Branch of the Bureau of Internal Revenue, Elmer L. Irey, to investigate mobster Al Capone in a later federal prosecution for tax evasion. Although earlier investigations regarding racketeering charges had been successfully defended by Capone, Irey believed Capone could be prosecuted under a 1927 ruling by the Supreme Court which declared that any income from criminal activities must be subjected to income taxes.

However, as Capone did not file tax returns, own property, endorse checks, maintain bank accounts or give receipts, his income could not be accounted for. As calculating Capone's net worth and expenditures were crucial to federal prosecutors, Wilson arranged to have Capone's organization, known as the "Chicago Outfit," to be infiltrated by federal agents to gather information on Capone's dealings in bootlegging, illegal gambling, and other vices.

Wilson himself moved into Chicago's Sheridan Plaza Hotel with his wife under the guise of a tourist. Wilson's wife was uninformed of the details of his assignment; instead she had been told that Wilson was investigating the finances of one "Curly Brown." Wilson would spend the next three years gathering information on Capone's financial dealings including tracking down mob accountants and bookkeepers.

Becoming aware of Wilson's investigation, a nervous Capone ordered five gunmen to murder Wilson. Federal authorities were informed of the contract and, after urgings from former mentor Johnny Torrio, Capone reluctantly canceled the hit. As a result of Wilson's investigation, which revealed millions of dollars in unreported income, Capone was eventually sentenced to 11 years of imprisonment.

Wilson was part of the team investigating the Lindbergh kidnapping. Some sources indicate that Wilson had insisted on tracking the serial numbers on the gold certificates used as ransom money (which ultimately led to the arrest and conviction of Bruno Richard Hauptmann).[1] Other sources credit Elmer Irey.[2]

In 1936, Wilson was named chief of the Secret Service and, resisting attempts by J. Edgar Hoover to transfer the Secret Service to the Justice Department under the jurisdiction of the FBI during the early 1940s, he had nearly eliminated the production and distribution of counterfeit money through a nationwide education program by the end of his retirement in 1947. During his administration, he also initiated practices in presidential security which have since become standard procedure.